First case report of mortality in an egg‐incubating boreal owl ( Aegolius funereus ) due to combined Yersinia pseudotuberculosis and Sarcocystis spp. infections

Abstract Records of lethal consequences from bacterial and parasitic infections in wildlife are scarce, and the conditions under which pathogens cause mortality in infected animals remain poorly understood. We report the first documented case of a female boreal owl ( Aegolius funereus ) incubating eggs that died on the nest due to a co‐infection with Yersinia pseudotuberculosis and Sarcocystis spp. This case highlights that co‐infections, particularly with highly virulent pathogens like Y. pseudotuberculosis , can severely impair animal fitness and reproductive survival, emphasising the need for comprehensive pathogen monitoring in wildlife populations.